1. Field of the Invention
The present invention relates to a color filter, a production process thereof and a liquid crystal display device equipped with the color filter.
2. Related Background Art
In recent years, the research and development of liquid crystal display devices as flat display panels have gone on expanding, and the markets of the liquid crystal display devices are being enlarged on a great scale.
Components making up a liquid crystal display device are roughly divided into polarizing plates, glass bases, orientation films, a liquid crystal material, spacers, a color filter and the like. Of these, the color filter is said to become a key point for permitting the provision of liquid crystal display devices at reasonable cost because it is relatively high in cost.
The color filter for liquid crystal display device is constructed by arranging a plurality of coloring members different in spectral characteristics from each other, generally, coloring members of red (R), green (G) and blue (B) colors on a transparent base. The coloring members function as pixels.
In order to enhance display contrast, light-screening members are provided between the pixels. These light-screening members are called black matrices because they are generally of a black color.
The black matrices are usually formed by subjecting a deposited film or sputtered film of metallic chromium to an etching treatment. Processes for forming the coloring members which make up the pixels include a process of dyeing a dyeable medium which has been formed using a photolithographic technique, a process of using a pigment-dispersed photosensitive composition, and an electrodeposition process making good use of a patterned electrode. Besides, as a forming process low in cost, there is a process making use of an ink-jet system.
The process of producing a color filter using the ink-jet system can reduce the production cost compared with the conventional processes of producing a color filter. However, the cost is not yet reduced to a fully satisfactory extent under the circumstances.
For example, Japanese Patent Application Laid-Open No. 4-123006 discloses a production process of a color filter, wherein a photosensitive resin layer and a silicone rubber layer are laminated on a transparent base, on which black matrices have been formed, other portions of the photosensitive resin layer and the silicone rubber layer than the areas, on which the black matrices have been formed, are removed using a photolithographic process, and coloring members are then arranged on the thus-exposed areas using an ink-jet system.
Japanese Patent Application Laid-Open No. 5-232313 discloses a production process of a color filter, which comprises the steps of first laminating a photosensitive resin layer and a silicone rubber layer on a transparent base, selectively removing the photosensitive resin layer and the silicone rubber layer using a photolithographic process to coat the exposed areas with light-screening members and then with an additional silicone rubber layer, removing other portions of the photosensitive resin layer and the silicone rubber layer than the areas on which the light-screening members have been provided, and then arranging coloring members on the thus-exposed areas using an ink-jet system.
The production processes of a color filter disclosed in the above publications involve problems to be solved. More specifically, the following two points must be solved.
Namely, (i) since the photolithographic process is used, a developing step is necessary subsequently to exposure, and so the process becomes complicated. Taking the cost of liquid crystal display devices at present into consideration, it is necessary to simplify a production plant and production steps to reduce production cost. (ii) Since the silicone rubber layer is laminated, a protective layer or the like cannot be applied thereon. When the protective layer or the like is applied, it is necessary to remove the silicone rubber layer. This removal step takes a relatively long time and must be improved for reduction of the cost. On the other hand, if no protective layer is applied, the insecurity of durability and stability in the resulting color filter may be caused in some cases.